This invention relates to tracheostomy valves, for use on tracheostomy tubes; it also relates to methods of restoring and improving the physiological function of patients who have tracheostomy tubes. The general background of the invention is described in Birch U.S. Pat. No. 3,844,290 and Tabor U.S. Pat. Nos. 3,137,299 and 4,325,366, which also exemplify the prior art. The prior art describes valves that tend to block passage of air outward through the tracheostomy tube during exhalation, but permit passage of air inward to the lungs through the tracheostomy tube during inhalation.
It has been discovered that a number of undesirable effects result from less than total blockage of airflow through a tracheostomy valve during all or part of the exhalation phase of the respiration cycle. Partial airflow through the valve during the exhalation phase is required by such inventions as that of Tabor U.S. Pat. No. 4,325,366, and is likely to occur with devices such as that of Birch U.S. Pat. No. 3,844,290. The passage of moisture-laden breath through the tracheostomy tube to the ambient atmosphere tends to produce deposits of moisture and mucus on the walls of the valve housing. Such deposits tend to increase friction, making the valve more difficult to open during inhalation. They may also act as a culture medium for pathogens, such as pseudamonas bacteria. Further, such valves tend to click and produce vibration in use, particularly at the beginning of the exhalation cycle, which disturbs the patient. Finally, the speech of users of such valves is not normal and is frequently unintelligible.
It is noted that some prior art devices, such as that of Tabor U.S. Pat. No. 3,137,299, may be considered to suggest providing a one-way tracheostomy valve that entirely blocks airflow during the exhalation phase, but they do not expressly teach that it is important or beneficial to do so. Moreover, other prior art devices, such as that of Tabor U.S. Pat. No. 4,325,366, expressly teach in the opposite direction, i.e., to leave a certain amount of valve opening so as to permit airflow at the beginning and end of the exhalation cycle. It is believed that no prior art device teaches that beneficial results occur in tracheostomized patients as a result of totally blocking airflow through the tracheostomy valve except during inhalation, and that no teaching exists of any structure expressly devised to insure such blockage.
It has been observed clinically that tracheostomized patients frequently have one or more of the following problems, adversely affecting their normal physiological function, and resulting from the tracheostomy:
(1) Loss of speech. This results from the diversion of air through the tracheostomy tube, bypassing the larynx and oral and nasal cavity.
(2) Loss of olfactory sensation. It is believed that this results from the same diversion of air. Loss of olfaction has an adverse effect on appetite, and may lead to loss of weight.
(3) Increased nasal and oral secretions. This results from the diversion of air away from the oral cavity and also from the diversion of air from the nasal cavity. The diverted air would otherwise have facilitated the evaporation of these secretions.
(4) Decreased oxygenation of blood. It is believed that this results from decreased pressure created in the alveoli of the lung, as a result of an open exit path (or lower resistance path) for air via the tracheostomy tube.
(5) Increased infections of respiratory tract. It is believed that this results from several causes. One is that finger occulusion of the neck is a common practice among tracheostomized patients; this practice occurs because patients are dissatisfied with, and therefore do not use, existing tracheostomy valves. Finger occulusion promotes infection, because of contaminating material that may be on the fingers. A second factor is lack of filtration of inhaled air, since it does not traverse the nasal cavity. It is believed that these factors promote pneumonitis. It is believed that another factor causing increased infection is the accumulation of moisture and mucus in existing tracheostomy devices, which provides a culture medium for pathogens. Increased oral and nasal secretions, noted above, may be a further causative factor of the same type.
(6) Difficulty in swallowing. This is associated with aspiration of food and fluids, and may lead to pneumonia or upper respiratory infections. Although it is not believed that the literature has associated this with particular characteristics of tracheostomy devices, the inventor believes that this results, as described below, from an imbalance of pressure within the throat, as a result of tracheostomization.
(7) Abnormal expectoration. It has been observed that tracheostomized patients expectorate into and through their tracheostomy tubes. When a person coughs, mucus, fluid, or other matter is expelled upward from the lungs to the trachea. In a normal person, this matter passes upward through the trachea past the epiglottis into the mouth, and is then expelled. In a tracheostomized patient, however, there is a low resistance parallel path through the tracheostomy tube. This permits matter to be driven from the lungs into the tube and at times to be ejected from the tube.
(8) Difficulty in decannulation. Decannulation is the removal of a tracheostomy tube, once the medial need for its presence had ended. It has been observed clinically that it is often difficult to decannulate patients, particularly pediatric patients, because the patients are afraid that they cannot breath without the tube. This makes it difficult to rehabilitate such patients.
These effects have not been correlated with particular characteristics or structures of tracheostomy tubes or related apparatus.